The largest used volume of Butyl polymers based on brominated isobutylene methyl styrene monomer (BIMSM), such as EXXPRO™ elastomer, is in the tire innerliner area. Air impermeability is the most important performance property of Butyl polymers in this application.
The idea of using nanoclay or organoclay to provide a step increase in impermeability of polymer is known. It has recently been discovered that increasing the amount of either brominated paramethyl styrene (BrPMS) or paramethyl styrene (PMS) content in BIMSM will result in the disappearance of the clay signal peak when X-ray experiment is performed on the blends of BIMSMs with several organoclays; (U.S. application Ser. No. 11/400,662, filed Apr. 7, 2006).
A common problem for nanocomposites in general is processability of the materials before cure, resulting in a high Mooney viscosity number measured at 125° C. This problem has conventionally been addressed by adding a processing oil or diluent in the compound to reduce viscosity. However, the cured nanocomposites containing oil or diluent will have a higher gas permeation rate, producing a deleterious effect on the barrier properties of the articles.
The present inventor has surprisingly discovered that the addition of tackifier to nanocomposites provides, in embodiments, compositions with improved performance in at least one of processability and barrier properties.